Oil and gas companies are continuing to pile up debt, a trend some warn could extend the slump in energy prices and hit economies reliant on the sector for growth and tax revenue. Both independent and state-owned companies are involved in the borrowing bonanza, issuing $86.8 billion worth of bonds in dollars, euros and yen globally this year, up 10% from the same period in 2014, according to Dealogic, a data-tracking company. The rise is largely due to a high number of bond sales in Europe, the Middle East and Africa, and in the U.S., where both Exxon Mobil Corp. and Chevron Corp. have recently tapped investors. The debt surge has been less dramatic in Asia. Still, China Petrochemical Corp., known as […]